D-shaped tube for header

ABSTRACT

Disclosed is a water cooled exhaust assembly for use in association with an internal combustion engine in a marine environment. Inner and outer nested tubes are affixed to a mounting flange to form, in conjunction with an access port in the mounting flange, a cooling water flow channel to provide cooling of exhaust gases from the engine. The inner tube is formed with a flattened portion to produce a reduction in exhaust gas turbulence in the flow channel with a consequent increase in heat transfer capability.

PRIORITY CLAIM

This application claims the benefit of previously filed U.S. Provisional Patent Application entitled “D-SHAPED TUBE FOR HEADER,” assigned U.S. Ser. No. 60/721,762, filed Sep. 29, 2005, and which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present subject matter relates to exhaust systems and, more particularly, to water cooled exhaust systems for marine applications.

BACKGROUND OF THE INVENTION

The incorporation of water cooling for exhaust systems for internal combustion engines has many advantages. While high temperature of the exhaust gases is desirable for high power output from the engine, high exhaust gas temperatures at the manifold place a high degree of stress on the manifold pipes. Moreover, under some conditions, hot combustion gases coming from an internal combustion engine may be combustible and potentially explosive. Thus, excess heat from the hot combustion gases must be continuously removed in order to maintain a suitable operating environment.

Excessively high temperatures can lead to premature failure of exhaust manifold assemblies, compromising the ability of the exhaust manifold assembly to remove the heat and exhaust gases from the engine and engine compartment. The provision of water cooled exhaust systems addresses many of these adverse conditions.

Yet another potential capability offered by water cooling of exhaust systems is the opportunity to employ diverse materials in the exhaust system. Commonly used exhaust systems rely on the use of steel and, in some instances, tungsten, but as improved engine designs develop higher power output, exhaust temperatures may well be higher than currently known. Thus, relying on more sophisticated and possibly more expensive materials to handle the hot exhaust gases is not a preferred solution.

A known solution for providing water cooled exhaust systems is found in U.S. Pat. No. 6,397,589 B1 to Beson et al. entitled Exhaust Pipes And Assemblies” and assigned to the owner of the present subject matter. In this known arrangement, manifold pipe assemblies and exhaust manifold assemblies, are optionally provided in combination with internal combustion engines, for receiving hot gases from such heat source, and conveying such hot gases from the heat source toward a lower temperature environment. Such manifold pipe assembly comprises a manifold pipe defining a gas path for conveying hot gases from an inlet end to an outlet end, and a jacket pipe encompassing the manifold pipe along a portion of the length of the manifold pipe. Such jacket pipe has a second inlet end disposed toward the inlet end of the manifold pipe, and a second outlet end disposed toward the outlet end of the manifold pipe. The jacket pipe is closed about the manifold pipe at the second inlet end, to form a closed cooling chamber between the manifold pipe and the jacket pipe. An inlet pipe conveys cooling liquid into the cooling chamber. A closed end chamber portion of the cooling chamber is defined optionally between the inlet pipe and a face of the cooling chamber disposed toward the manifold end of the manifold pipe, sufficiently close to the inlet end of the cooling chamber in combination with the closed end chamber portion being suitably configured, as to maintain sufficient flow of cooling liquid at the inlet end, into and through the closed end chamber portion, to preclude development of localized hot spots on the manifold pipe adjacent the cooling chamber when cooling water is routinely passing through the cooling chamber during routine operating conditions of the pipe assembly. Some embodiments preferably include an enlarged section of the cooling chamber proximate or at the inlet end of the cooling chamber, which acts as an accumulation reservoir for increasing residence time of the cooling liquid therein, thereby to absorb additional heat from the manifold pipe adjacent the inlet end of the cooling chamber.

Another known solution for providing exhaust systems in combination with water cooling features is found in U.S. Pat. No. 5,820,426 to Hale, entitled “Exhaust System For Personal Watercraft.” In this known arrangement, an exhaust system for a personal watercraft provides an exhaust adapter plate and an exhaust header pipe that allows exhaust to exit from the rear of a horizontally mounted internal combustion engine. The exhaust adapter plate is mounted to the rear of the engine block. The exhaust adapter plate has openings corresponding to the engine exhaust port and engine cooling water jacket. The adapter plate also has an opening for the engine crankshaft. The exhaust header pipe is mounted to the engine with the adapter plate disposed therebetween. An exhaust passage through the exhaust header pipe passes transversely across the engine compartment within the watercraft. As the exhaust header pipe passes transversely across the engine compartment, the exhaust passage angles upwardly from the exhaust adapter plate to a high point, and angles downwardly from the high point to an exhaust outlet leading to a muffler. The exhaust passage through the exhaust header pipe is tuned, yet the configuration of the exhaust header pipe provides a compact design that is easily packaged within the engine compartment for a personal watercraft, and also provides for sufficient space rearward of the exhaust header pipe so that the exhaust system and the remainder of the engine can be easily serviced.

U.S. Pat. No. 6,672,919 is another patent to Beson, and is entitled “Temperature Control System for Marine Exhaust.” A temperature control system for a marine engine exhaust system is provided in such arrangement. The control system lowers the flow of cooling water to the water jacket and exhaust gas conduit of the exhaust system at low engine speeds. Such control can operate in an on/off mode, or can modulate rate of flow of water through the exhaust system, or both. However the water flow is limited, a predetermined minimum flow of cooling water is maintained through the exhaust system, at least either at periodic intervals, or at a constant but lowered rate, to maintain cooling in the exhaust system on rubber components of the exhaust system.

Still another known arrangement is provided by U.S. Pat. No. 6,609,590 to Zelinski, and entitled “Exhaust System Having Angled Baffle.” In such arrangement, in-line exhaust systems comprise an exhaust pipe, and a sound-attenuating baffle in the exhaust pipe. The baffle has one or more baffle plates extending across the gas flow channel, at least one at an oblique angle. Each plate has an array of apertures therethrough. The plates are joined to each other, preferably in edge-to-edge relationship, preferably forming included angles with each other and forming preferably different, oblique angles to the longitudinal axis. In preferred embodiments, plate aperture area increases, plate-to-plate, along the direction of advance of gases in the exhaust system. A backwash valve can lie over one of the baffle plates. The exhaust system can include a water jacket, and optionally an outer sound attenuation chamber. The baffle is preferably 36 or less inches long, the exhaust system reducing noise by at least 3 decibels.

Another known arrangement is provided by U.S. Pat. No. 6,883,312 to Lindholm, and entitled “Water Cooled Exhaust Tube.” Per such arrangement, a combustion engine, such as an Otto engine or diesel engine for land and water vehicles, has an exhaust system with an exhaust catalyst integrated into the exhaust pipe, and a catalyst cooling device fed with a fluid or pasty coolant, preferably water, glycerin or a gel. Also provided is a silencer, especially for such a combustion engine, having a silencer cooling device fed with a fluid or pasty coolant. The cooling device may form a housing for either the catalyst or for the silencer.

The disclosures of the foregoing patents are fully incorporated herein for all purposes.

While various implementations of a water cooled exhaust system exist, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.

SUMMARY OF THE INVENTION

In view of the recognized features encountered in the prior art and addressed by the present subject matter, an improved methodology is presented for providing water cooling for exhaust systems for internal combustion engines.

In an exemplary configuration, an assembly of nested exhaust and cooling jacket pipes is provided in combination with an exhaust manifold attachment flange that simplifies coupling of both exhaust emissions and cooling water to the assembly.

In one of its simpler forms, the water cooled exhaust assembly in accordance with certain embodiments of the present technology corresponds to a welded assembly of nested stainless steel pipes configured to pass exhaust gases through the relatively inner pipe, to permit cooling water to flow between an outer surface of such inner pipe and an inner surface of a relatively outer pipe, and to commingle the exhaust gases and cooling water at an outlet end of the assembly.

In accordance with aspects of certain embodiments of the present subject matter, methodologies are provided to reduce the turbulence of the cooling water flow between the exhaust pipe and jacket pipe to improve heat transfer from the exhaust gases to the cooling water.

In accordance with further certain aspects of other embodiments of the present subject matter, methodologies have been developed to improve heat transfer to the cooling water by providing shaped correspondence between the walls of the nested exhaust pipe and jacket pipe to enhance the cooling water flow characteristics.

In one present exemplary embodiment, a water cooled exhaust assembly preferably comprises an outer tube portion, an inner tube portion having a generally free end thereof, and a mounting flange for supporting such assembly relative to an associated internal combustion engine. Additionally, there is provided at least one cooling water entrance port formed in the mounting flange, and at least one cooling water exit port formed in the outer tube portion. In such preferred exemplary embodiment, preferably the inner and outer tube portions are configured for the inner tube portion to pass exhaust gases from an associated internal combustion engine while a space is formed between the inner and outer tube portions for defining a cooling water channeling system in conjunction with the entrance and exit ports. Still further in such exemplary embodiment, preferably the inner and outer tube portions have predetermined shaped correspondence between the walls thereof, for reducing turbulence of the flow characteristics of cooling water passing therethrough, for improved heat transfer characteristics.

In the foregoing exemplary water cooled exhaust assembly, such inner tube portion may preferably define a relatively flattened area thereof, to provide such predetermined shaped correspondence. Still further, such relatively flattened area of such inner tube portion may be generally near an end thereof relatively adjacent to the mounting flange. Yet another aspect of such an exemplary water cooled exhaust assembly may be that the inner tube portion defines an angled cut portion therethrough adjacent the relatively flattened area thereof, to collectively form a relatively “D” shaped opening therein.

Another present exemplary water cooled exhaust system for internal combustion engines may preferably comprise an assembly of nested exhaust and cooling jacket pipes, and an exhaust manifold attachment flange, for simplified coupling of both exhaust emissions and cooling water to such assembly. In such assembly, preferably the nested pipes have a predetermined shape between the walls thereof, for improved heat transfer characteristics by reducing turbulence of the flow characteristics of cooling water passing therethrough, for more efficient heat transfer.

In such a present exemplary system, the nested pipes further preferably may include respective inner and outer tube portions, the inner tube portion may define a relatively flattened area thereof generally near an end thereof relatively adjacent to the attachment flange, and the inner tube portion defines an angled cut portion therethrough adjacent such relatively flattened area thereof, to collectively form a relatively “D” shaped opening therein.

Additional features may be alternatively practiced with various of the foregoing exemplary embodiments, to form yet further present embodiments.

Yet another present exemplary embodiment relates to methodology, including for example methodology for improved heat transfer from exhaust gases of an internal combustion engine to cooling water in a water cooled exhaust system of the type having an assembly of nested pipes, such assembly having an inlet end, an outlet end, and respective relatively inner and outer pipes thereof, and configured to pass exhaust gases of the internal combustion engine through the relatively inner pipe thereof, and to permit cooling water to flow between an outer surface of such inner pipe and an inner surface of the relatively outer pipe thereof. Such improved methodology preferably includes providing predetermined shaped correspondence between the walls of the nested pipes to reduce the turbulence of the cooling water flow between the nested inner and outer pipes, which in turn improves heat transfer to the cooling water. Still further, per such present methodology, it may be included that providing the predetermined shaped correspondence comprises defining a relatively flattened area in said inner pipe. In certain present embodiments, such methodology of defining a relatively flattened area in such inner pipe may also include includes defining such relatively flattened area generally near an end of the inner pipe relatively adjacent to the assembly inlet end.

Additional objects and advantages of the present subject matter are set forth in, or will be apparent to, those of ordinary skill in the art from the detailed description herein. Also, it should be further appreciated that modifications and variations to the specifically illustrated, referred and discussed features and elements hereof may be practiced in various embodiments and uses of the present subject matter without departing from the spirit and scope of the subject matter. Variations may include, but are not limited to, substitution of equivalent means, features, or steps for those illustrated, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.

Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of the present subject matter may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features, parts, or steps or configurations thereof not expressly shown in the figures or stated in the detailed description of such figures). Additional embodiments of the present subject matter, not necessarily expressed in the summarized section, may include and incorporate various combinations of aspects of features, components, or steps referenced in the summarized objects above, and/or other features, components, or steps as otherwise discussed in this application. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the remainder of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIGS. 1(a), 1(b), and 1(c) are rear, front oblique, and top perspective views, respectively, of an exemplary assembled water cooled exhaust assembly in accordance with the present technology;

FIGS. 2(a), 2(b), and 2(c) are side elevation, rear elevation, and rear oblique perspective views, respectively of an exemplary inner tube portion of the present exemplary water cooled exhaust assembly in accordance with the present technology;

FIGS. 3(a), 3(b), and 3(c) are respectively top, bottom, and side oblique perspective views of an exemplary flange portion of the present exemplary water cooled exhaust assembly in accordance with the present technology;

FIGS. 4(a), 4(b), and 4(c) are front plan, side plan, and rear oblique perspective views, respectively, of an exemplary outer tube portion of the present exemplary water cooled exhaust assembly in accordance with the present technology; and

FIG. 5 is a partially cutaway view of the present exemplary water cooled exhaust assembly illustrating an exemplary water flow path.

Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the present subject matter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As discussed in the Summary of the Invention section, the present subject matter is particularly concerned with improved arrangements and methodology for providing water cooling for exhaust systems for internal combustion engines.

Selected combinations of aspects of the disclosed technology correspond to a plurality of different embodiments of the present subject matter. It should be noted that each of the exemplary embodiments presented and discussed herein should not insinuate limitations of the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to yield yet further embodiments. Additionally, certain features may be interchanged with similar devices or features not expressly mentioned which perform the same or similar functions.

Reference will now be made in detail to the presently preferred embodiments of the subject water cooled exhaust system. Referring now to the drawings, FIGS. 1(a), 1(b) and 1(c) illustrate various respective views of a water cooled exhaust assembly 100 in accordance with the present technology. Assembly generally 100 corresponds to three major components that are combined together (for example, with welding) to form an exemplary complete present assembly 100 having a generally free end 110. Such three major components correspond to an outer tube portion generally 120, an inner tube portion generally 130, and a mounting flange generally 140. The inner tube portion 130 is configured to pass exhaust gases from an associated internal combustion engine (not illustrated) while the space between the inner tube portion 130 and outer tube portion 120 carries cooling water passing through a channeling system created by the nested inner and outer tube portions as well as access ports in the mounting flange 140 and exit ports 122, 124 of the outer tube portion 120.

With further reference to FIGS. 1(a)-1(c), it will be seen that mounting flange 140 has machined therein a number of holes 142 through which bolts (not illustrated) may be passed to mount the assembly 100 to an internal combustion engine. In addition, mounting flange 140 includes a port 144 (FIG. 1(a)) through which cooling water may pass, as will be further described herein with respect to FIGS. 3(a)-3(c).

With reference now to FIGS. 2(a), 2(b), and 2(c), there is illustrated an inner tube portion generally 130 of the water cooled exhaust system in accordance with the present technology. A significant aspect to such inner tube portion 130 may be seen in the provision of a relatively flattened area generally 132 (best seen in FIGS. 2(b) and 2(c)) on the rear portion of the inner tube portion 130. In conjunction with an angled cut through inner tube portion 130, such flattened portion 132 forms a relatively “D” shaped opening 134 having a substantially linear portion 136 of the “D” shape adjacent flattened portion 132 of the inner tube portion 130.

Flattened portion 132 of inner tube portion 130 operates together with outer tube portion 120 to form a portion of a water flow channel from port 144 of flange portion 140, which extends from where end portion 138 of inner tube portion 130 joins with flange portion 140, and through the space between nested inner tube portion 130 and outer tube portion 120. The flat shape resulting from flattened portion 132 and cooperating with the inner surface of outer tube portion 120, contributes to a significant reduction in turbulence in the cooling water flowing through the space between the inner and outer tube portions, 130 and 120 respectively. As the level of turbulence in the flowing cooling water decreases, the opportunity for heat transfer from the hot exhaust gases contained in the inner tube portion 130 to the cooling water increases, resulting in a more efficient heat transfer capability.

With reference to FIGS. 3(a)-3(c), there are illustrated various respective views of the flange portion 140 of a present exemplary water cooled exhaust assembly generally 100 in accordance with the present technology. As best seen by comparison of the generally top and bottom perspective views of flange 140 in FIGS. 3(a) and 3(b), respectively, water access port 144 is configured in the top portion (FIG. 3(a)) so as to correspond to a generally “C” shaped configuration 146, so as to correspond with the general shape of the end 138 of the inner tube portion 130, as will be described further with reference to FIG. 5. The shape of water access port 144 appears from the bottom portion (FIG. 3(b)) of flange 140 as an elongated oval 148, through which “C” shaped portion 146 may be partially seen.

With reference to FIGS. 4(a)-4(c), there are illustrated various views of the outer tube portion generally 120 of the present exemplary water cooled exhaust assembly generally 100 in accordance with the present technology. Outer tube portion 120 is generally round in diameter and has a cut through portion 126 terminating in an end portion 128 generally corresponding in cut angle to the similarly shaped portion of inner tube portion 130. The exit end portion of outer tube portion 120 is particularly characterized by the inclusion of access portion 122 and 124. As may best be seen in FIGS. 4(a) and 4(c), such access portions 122, 124 correspond, respectively, to a cut out portion 122 of the exit portion of outer tube portion 120, and to a through hole 124 machined into the exit portion of outer tube portion 120 on a side of outer tube portion 120 generally opposite that of cut out portion 122.

As may best be seen from the fully assembled views illustrated with FIGS. 1(c) and 5, cut out portion 122 of outer tube portion 120 cooperates with inner tube portion 130 to form an exit outlet for cooling water flow through the space formed between the inner tube portion 130 and outer tube portion 120. In addition, through hole 124 provides a supplemental exit port for cooling water flow.

With reference to FIG. 5, a partially cutaway illustration of the present exemplary assembled water cooled exhaust assembly is illustrated in order to better visualize the relationship among the inner tube portion 130, the outer tube portion 120, and the access port 144 in flange portion 140, all with respect to the formation of the present cooling water flow channel. As illustrated in FIG. 5, end portion 138 of inner tube portion 130 is positioned adjacent the inner portion of “C” shaped portion 146 in the top portion of flange 140. Although not illustrated herein, inner tube portion 130 may be welded to flange portion 140 in a sealing relationship.

Outer tube portion 120 is positioned such that end portion 128 thereof is positioned adjacent the outer portion of “C” shaped portion 146 of access port 144 in the top portion of flange 140. As with inner tube portion 130, outer tube portion 120 may be welded to flange portion 140 in a sealing relationship, thereby forming with inner tube 130 a cooling water flow channel as discussed herein.

While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art. 

1. A water cooled exhaust assembly, comprising: an outer tube portion; an inner tube portion having a generally free end thereof; and a mounting flange for supporting said assembly relative to an associated internal combustion engine; at least one cooling water entrance port formed in said mounting flange; and at least one cooling water exit port formed in said outer tube portion; wherein said inner and outer tube portions are configured for said inner tube portion to pass exhaust gases from an associated internal combustion engine while a space is formed between said inner and outer tube portions for defining a cooling water channeling system in conjunction with said entrance and exit ports; and wherein said inner and outer tube portions have predetermined shaped correspondence between the walls thereof, for reducing turbulence of the flow characteristics of cooling water passing therethrough, for improved heat transfer characteristics.
 2. A water cooled exhaust assembly as in claim 1, wherein said inner tube portion defines a relatively flattened area thereof, to provide said predetermined shaped correspondence.
 3. A water cooled exhaust assembly as in claim 2, wherein said relatively flattened area of said inner tube portion is generally near an end thereof relatively adjacent to said mounting flange.
 4. A water cooled exhaust assembly as in claim 3, wherein said inner tube portion defines an angled cut portion therethrough adjacent said relatively flattened area thereof, to collectively form a relatively “D” shaped opening therein.
 5. A water cooled exhaust assembly as in claim 1, further including at least a second water cooling exit port formed in said outer tube portion.
 6. A water cooled exhaust assembly as in claim 1, wherein said outer and inner tube portions and said mounting flange are all welded together.
 7. A water cooled exhaust assembly as in claim 1, wherein said mounting flange has a plurality of bolt holes formed therein, for securing said mounting flange to an associated internal combustion engine.
 8. A water cooled exhaust assembly as in claim 1, wherein said at least one cooling water entrance port formed in said mounting flange has a generally “C” shaped configuration.
 9. A water cooled exhaust system for internal combustion engines, comprising: an assembly of nested exhaust and cooling jacket pipes; and an exhaust manifold attachment flange, for simplified coupling of both exhaust emissions and cooling water to said assembly; wherein said nested pipes have a predetermined shape between the walls thereof, for improved heat transfer characteristics by reducing turbulence of the flow characteristics of cooling water passing therethrough, for more efficient heat transfer.
 10. A water cooled exhaust system as in claim 9, wherein: said nested pipes include respective inner and outer tube portions; said inner tube portion defines a relatively flattened area thereof generally near an end thereof relatively adjacent to said attachment flange; and wherein said inner tube portion defines an angled cut portion therethrough adjacent said relatively flattened area thereof, to collectively form a relatively “D” shaped opening therein.
 11. A water cooled exhaust system as in claim 9, wherein said attachment flange further includes at least one cooling water entrance port formed in said mounting flange, and having a generally “C” shaped configuration.
 12. A water cooled exhaust system as in claim 9, wherein: said attachment flange includes at least one cooling water entrance port formed therein; said nested pipes include respective inner and outer tube portions; said inner tube portion has an angled cut therethrough adjacent an end thereof relatively adjacent said attachment flange, and having a relatively flattened sidewall portion thereof, collectively forming a relatively “D” shaped opening; and said relatively flattened portion of said inner tube portion is operative together with said outer tube portion so as to form a portion of a water flow channel from said cooling water entrance port of said attachment flange, and extending from where an end portion of said inner tube portion is joined with said attachment flange, and through a defined space formed between said nested inner and outer tube portions, such that said relatively flattened portion cooperating with the inner surface of said outer tube portion contributes to a significant reduction in turbulence in the cooling water flowing through the defined space between said inner and outer tube portions, with a corresponding improved opportunity for heat transfer from hot exhaust gases in said inner tube portion to the cooling water.
 13. A water cooled exhaust system as in claim 12, wherein: said outer tube portion is generally round in diameter and has a cut through portion thereof and terminating in an end portion thereof generally corresponding in cut angle to a similarly shaped portion of said inner tube portion, with an exit end portion of said outer tube portion defining two access portions formed, respectively, as a cut out portion of said exit portion of said outer tube portion, and as a through hole formed in the exit portion of said outer tube portion on a side thereof generally opposite that of said cut out portion thereof; and wherein said cut out portion of said outer tube portion cooperates with said inner tube portion to form an exit outlet for cooling water flowing through the space formed between said respective inner and outer tube portions while said an additional opening is defined in said outer tube portion to provide a supplemental exit port for cooling water flow.
 14. A methodology for improved heat transfer from exhaust gases of an internal combustion engine to cooling water in a water cooled exhaust system of the type having an assembly of nested pipes, such assembly having an inlet end, an outlet end, and respective relatively inner and outer pipes thereof, and configured to pass exhaust gases of the internal combustion engine through the relatively inner pipe thereof, and to permit cooling water to flow between an outer surface of such inner pipe and an inner surface of the relatively outer pipe thereof, the improvement methodology comprising providing predetermined shaped correspondence between the walls of the nested pipes to reduce the turbulence of the cooling water flow between the nested inner and outer pipes, which in turn improves heat transfer to the cooling water.
 15. A methodology as in claim 14, wherein such providing the predetermined shaped correspondence comprises defining a relatively flattened area in the inner pipe.
 16. A methodology as in claim 15, wherein such defining a relatively flattened area in the inner pipe includes defining the relatively flattened area generally near an end of the inner pipe relatively adjacent to such assembly inlet end.
 17. A methodology as in claim 14, wherein such providing the predetermined shaped correspondence comprises defining a relatively flattened area in the inner pipe, with an angled cut portion through such inner pipe and adjacent the relatively flattened area thereof, so as to collectively form a relatively “D” shaped opening in such inner pipe. 